gecko-dev/dom/canvas/test/imagebitmap_structuredclone.js

function ok(expect, msg) {
  postMessage({ type: "status", status: !!expect, msg });
}

onmessage = function(event) {
  ok(!!event.data.bitmap1, "Get the 1st ImageBitmap from the main script.");
  ok(!!event.data.bitmap2, "Get the 2nd ImageBitmap from the main script.");
  ok(!!event.data.bitmap3, "Get the 3rd ImageBitmap from the main script.");

  // send the first original ImageBitmap back to the main-thread
  postMessage({ type: "bitmap1", bitmap: event.data.bitmap1 });

  // create a new ImageBitmap from the 2nd original ImageBitmap
  // and then send the newly created ImageBitmap back to the main-thread
  var promise = createImageBitmap(event.data.bitmap2);
  promise.then(
    function(bitmap) {
      ok(
        true,
        "Successfully create a new ImageBitmap from the 2nd original bitmap in worker."
      );

      // send the newly created ImageBitmap back to the main-thread
      postMessage({ type: "bitmap2", bitmap });

      // finish the test
      postMessage({ type: "finish" });
    },
    function() {
      ok(
        false,
        "Cannot create a new bitmap from the original bitmap in worker."
      );
    }
  );

  // send the third original ImageBitmap back to the main-thread
  postMessage({ type: "bitmap3", bitmap: event.data.bitmap3 });
};